1. Field of the Invention
The present invention relates to an electric connection box for connecting wire harnesses to each other, particularly relates to an electric connection box capable of reducing portions of bringing about leakage between bus bars having different voltages.
2. Related Art
An electric connection box for connecting wire harnesses to each other is provided with a case main body comprising an upper case and a lower case, bus bar circuit boards are contained at inside of the case main body in a state of being laminated in the form of a number of layers and the electric connection box (bus bar circuit board) is arranged in a vertical direction. Each of the bus bar circuits which are actually used is constructed by a constitution as shown by FIG. 3 although not clearly disclosed as a technical literature. That is, a bus bar circuit board 1 is constituted by arranging a bus bar 3 for supplying low voltage and a bus bar 4 for supplying high voltage to an insulating board 2 constituted by an insulating material. Although not illustrated, the bus bar 3 and the bus bar 4 are provided with pluralities of branch tabs in a direction orthogonal to the bus bar circuit board 1, the branch tabs are projected to an outer face of the upper case or the lower case by penetrating tab inserting holes of the insulating board 2, contained to align at insides of various coupling portions of a connector coupling portion, a fuse coupling portion, a relay coupling portion and the like and connected to parts of a connector, a fuse, a relay and the like of wire harness terminals. The insulating board 2 includes a bus bar arranging groove which is formed to partition by a rib 5 opposed to a plate face thereof and the bus bar 3 and the bus bar 4 arranged to the bus bar arranging groove are fixed by welding bosses.
According to an embodiment of an electric connection box 20 of the invention illustrated in FIG. 1, a bus bar circuit board 1 constituted by arranging a plurality of bus bars 3 and 4 having at least two kinds of different potentials on an insulating board 2 is arranged vertically (in FIG. 1, arrange an upper side thereof to an upper side in a vertical direction) by arranging the electric connection box in a vertical direction and in arranging a bus bar 3A-1 and a bus bar 4A at which the bus bar 3 having low potential and the bus bar 4 having high potential are installed contiguous to each other in a horizontal direction, the bus bar 3A-1 having low potential is arranged on an upper side of the bus bar 4A having high potential in the vertical direction.
According to such a conventional bus bar circuit board 1, the bus bar 3 and the bus bar 4 are installed at the insulating board 2 without giving consideration to a potential difference of voltages respectively supplied thereto. Therefore, in the bus bar circuit board 1, the bus bar 3 and the bus bar 4 are not arranged on the insulating board 2 in a regular state.
In such a bus bar circuit board 1, when moisture invades inside of the electric connection box, leakage occurs at bus bar intervals 6A, 6B and 6C at which the bus bar 3 and the bus bar 4 arranged at the insulating board 2 are contiguous to each other. The occurrence of leakage at the bus bars produces an oxidation product of copper at the bus bars 3 and 4. The oxidation product of copper is frequently produced at the bus bar 4 supplying high voltage.
The oxidation product of copper is in a powder-like shape and therefore, as shown by FIG. 4 and FIG. 5, the oxidation product of copper flows between the bus bar 3 and the bus bar 4 by riding over the rib 5 at the bus bar intervals 6A, 6B and 6C by moisture 7 invading the electric connection box. Further, the oxidation product of copper is electrically conductive and therefore, when the oxidation product of copper flows by riding over the rib 5 at the bus bar intervals 6A, 6B, 6C and 6D along with the moisture, there is a concern that shortcircuit (shortcircuit) is brought and arc (spark) is generated between the bus bar 3 and the bus bar 4. When arc (spark) is generated in this way, there is a concern of effecting adverse influence on an element, apparatus or the like connected thereto.
Particularly, at the bus bar interval 6A illustrated in FIG. 3, there is a case in which the bus bar 4A having high voltage is arranged on an upper side of a position of the bus bar 3A-1 having low voltage in a vertical direction illustrated by an arrow mark. In this case, the oxidation product of copper produced at the bus bar 4A having high potential flows along with invading moisture, rides over the rib and flows to the side of the bus bar 3A-1 having low potential. Therefore, there is a possibility of bringing about shortage (shortage) and generating arc (spark) between the bus bars by presence of potential difference between the bus bar 4 and the bus bar 3 at the bus bar interval 6A.